Home – Home – Jornals – Journal of Applied Mechanics and Technical Physics 2022 number 6

The effect of changes in the thermophysical properties of the molybdenum film during intermediate oxidation during laser ablation on the dimensional effect of track formation is investigated by numerical simulation. In accordance with the data obtained, the hypothesis explaining the reduction of the track width in the ablation zone of the film in comparison with the effective diameter of the laser beam is refined. It is shown that a specific change in the thermal conductivity coefficient of a substance at the time of oxidation has a significant effect on the distribution of the temperature field, expressed in narrowing of the characteristic of the temperature distribution over the film surface, which has not been previously considered. It is established that the change in the density, specific heat capacity, and thermal effect of the chemical reaction of molybdenum oxidation during film oxidation does not significantly affect the temperature distribution in the zone of exposure to the laser beam.

The features of formation of face images of extended absolutely slit objects with an arbitrary opening of holes are studied in a coherent-optical system. On the base of the constructive approximation of the spectra of spatial frequencies (Fraunhofer diffractional patterns) of objects with different dimensions of front and back apertures, formulas for the field in the image of the front face are obtained and analyzed. Cases of objects with significantly expanding and significantly narrowing apertures of an extended hole (the differences in aperture sizes are much larger than the size of the Fresnel zone) are investigated in detail. It is found that the image structure of faces depends on the type of the opening. With a positive opening, where the back face is in the shadow region, the field at the output of the system corresponds to the image of the front face; with a negative opening, the image of the back face is observed. It is shown that error of determination of boundaries in the image of the active face of the object is inversely proportional to the square of the aperture difference. The invariant properties of the projection system for forming images of external faces of extended holes with an arbitrary opening are analyzed.

Design principles for the implementation of an infrared microscope registering the intrinsic thermal radiation of objects are considered. The infrared microscope temperature resolution, depending on the optical system parameters, design and photoelectric parameters of multielement infrared focal plane arrays (IR FPAs) are analyzed.

An equation of the dynamics of formation and radiation of a quasi-empty oscillating cylindrical cavity in a fluid is derived for the first time with due allowance for the changes in the velocity of sound and the volume fraction of cavitation nuclei. A dimensionless formulation of the problem is proposed and analyzed under the condition of identical pressures in the cavitation zone and inside the cylindrical cavity at its boundary. As a result, a dynamic relationship between the volume fraction (velocity of sound) in the cavitation zone and the radius of the cylindrical cavity is found.

A non-stationary electrohydrodynamic model has been developed to describe the behavior of a dielectric liquid film on the electrode surface in the surrounding gas. It has been shown that the action of an inhomogeneous electric field can lead to perforation of the film with the formation of new contact lines. The field inhomogeneity was created using a round insulating insert in the center of the lower electrode. The perforation process is determined by the electric field strength, film thickness, the radius of the non-conductive insert, and the contact angle between the liquid and the solid substrate.

In the present study, the effect of operating pressure on the flame response is investigated numerically, and the validity of atmospheric tests is examined. The results show that the flame shape significantly varies at atmospheric pressure, and the flame response to imposed pressure fluctuations is changed; therefore, atmospheric test stands are not reliable enough to study the combustion instability.

This paper presents a method for determining the gas-dynamic parameters of gas flow based on nonintrusive PIV measurements of the velocity field. The wake flow past a model single nozzle of an emergency escape rocket is considered for the normal transonic (Mach number is 0.85) flight mode of a launch vehicle with a manned spacecraft. The flow around the nozzle is simulated numerically using the RANS and LES methods. The results obtained by the proposed method are compared with numerical and experimental data.

Results of an experimental study of blood properties are reported. To approach the boundary conditions of blood biophysics in a real flow, the viscoelastic measurements are carried out on surfaces coated with a 10-nm thick fibrous layer composed of extracellular matrix protein. For native whole blood, a plateau of the shear elastic modulus as a function of frequency is observed. It is concluded that a slow flow of blood plasma close to the vessel wall can generate a stationary plasma layer that contributes to the functional width of surface layers in blood vessels. The shear stress term calculated from the wall shear rate and blood viscosity becomes imprecise if it does not include the existence of this intermediate layer.

A nanoscale calculation is performed for water permeation through the cell membrane in a human body, which is 7-8 nm thick and contains densely distributed nanopores with the radii ranging between 0.2 and 0.5 nm. The pressure drop and the critical power loss on a single nanopore for initiating the wall slippage are calculated. The wall slipping velocity is found to increase significantly with reduction of the pore radius and to increase linearly with an increase in the power loss on the pore. For no wall slippage, the water mass flow rate through the pore is significantly lower than the classical hydrodynamic flow theory calculation; however, it is much greater (by three to five orders of magnitude) than the classical hydrodynamic flow theory calculation in the case where the wall slippage occurs. This water flow enhancement is heavily dependent on the power loss on the pore.

The current study focuses on the influence of thermal boundary conditions, especially for a ribbed cooling channel with two intersecting ribs. Numerical studies are carried out for the Reynolds number of 30000 under two kinds of thermal boundary conditions, i.e., the constant wall temperature condition and the uniform heat flux condition. The local normalized Nusselt number distributions and area-averaged values are compared and further analyzed. The thermal boundary type and value both affect the heat transfer performance. The uniform heat flux condition always yields higher heat transfer than the constant wall temperature condition. A correlation for the wall-to-coolant temperature ratio is obtained and compared with previously published correlations.

The two-dimensional Green-Naghdi equations are investigated in the case of an uneven bottom topography. The function which determines the topography of the bottom and may depend on time is considered. A group classification of the equations under study with respect to the function describing the bottom topography is carried out using an algebraic approach.

Results of an experimental and numerical study of a supersonic flow around a cylinder with a gas-permeable cellular-porous frontal insert aligned at various angles of attack are reported. The experiments are performed in the T-327 wind tunnel based at the Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences at the Mach number of 7 and Reynolds number of 1.5x106 m-1. The forces and moments are measured on models with diameters of 10.0, 14.5, 24.0, and 34.0 mm. The models are equipped with porous inserts whose length is equal to two diameters of the cylinder, the porosity value is 95%, and the pore diameters are 1, 2, 3, and 4 mm. The angle of attack is varied in the interval 0-25oC. The numerical simulations are performed by means of solving three-dimensional Reynolds-averaged Navier-Stokes equations with the use of the (k-ω)SST turbulent model and a toroidal skeleton model of the porous material. Based on generalization of experimental and numerical data for the normalized drag coefficient at various angles of attack, empirical dependences of this quantity on the similarity parameter including the ratio of the pore diameter to the cylinder diameter and the Mach number are derived.

Results of methodical activities on optimization of computations of the laminar-turbulent flow on various computational grids aimed at saving computational resources are reported. The study is performed on the basis of data calculated for a supersonic flow around a swept wing in a virtual wind tunnel with the use of the ANSYS Fluent CFD software with an additional package for determining the laminar-turbulent transition developed at the Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences on the basis of the e^N method.

A problem of rotation of a fluid layer bounded by a solid plane and a free surface parallel to this plane is considered. The fluid can be an ideal or a viscous fluid. Conditions for the existence of solutions of the corresponding problems for the Euler and Navier-Stokes equations on an infinite time interval are formulated. Examples of the numerical solution of the problem are presented.

For a non-linear parabolic reaction-diffusion system, solutions of the diffusion wave type are constructed and investigated. For the first time, the formulation of the problem is considered, which involves the assignment of non-coinciding zero fronts for various desired functions. A theorem on the existence and uniqueness of solutions in the form of series in the class of piecewise analytic functions is proved. To construct approximate solutions of the desired type, a step-by-step iterative algorithm based on the collocation method and expansion in radial basis functions is proposed. Calculations were performed, for the verification of the results of which segments of the series were used. A numerical analysis of the behavior of the constructed solutions was carried out.

The paper considers the mechanism of reducing the permeability of aqueous graphene suspension through the oil-saturated core compared to distilled water. Analysis of experimental data shows that an increase in permeability is due to the formation of corrugated films at the interface between two immiscible fluids during their mutual motion. The appearance of wavy surfaces is the result of Kelvin-Helmholtz instability at the grapheme-nanofluid-hydrocarbon interface. It is also shown that the occurrence of instability is possible only in the presence of a transition layer-graphene film.

Two nonlinear models are proposed that describe the formation and evolution of the mixing layer between two codirectional stratified fluid flows based on a three-layer flow representation in the long-wavelength approximation. The models are similar in structure, and in Boussinesq approximation, the equations of motion are written in a uniform way in the form of a system of inhomogeneous conservation laws. The speeds of propagation of perturbations are determined, and the concept of subcritical (supercritical) flow is formulated. Continuous and discontinuous solutions of the models are constructed. It is shown that for a sufficiently large difference between the velocities of codirectional flows, the stationary mixing layer expands monotonically and the maximum entrainment mode occurs. With a decrease in the initial difference in the velocities of the cocurrent flows, an oscillating stationary solution is obtained and the structure of the mixing layer becomes wavy. For one of the flow modes, the obtained solutions are compared with experimental data.

A problem of internal waves in a two-layer stratified fluid with a density that depends exponentially on the depth inside the layers and has a jump at the interface is considered. An equation for the second long-wavelength approximation is derived, which describes solitary waves. The spectral properties of the equations of small perturbations of a horizontal piecewise constant flow are studied and the possible mechanisms for the occurrence of shear instability of a stratified flow are characterized.

A technique for manufacturing a metal composite material from Ti64 titanium alloy reinforced with SiC ceramic fibers using surface laser cladding technology is proposed. The influence of the parameters of laser action on the shape of a single track is studied. The stability of the formed composite material under high-speed impact has been studied. It is shown that for a sample reinforced with ceramic fibers, the depth of the crater in the substrate is 37% less than for a sample made of Ti64 alloy.

A technique has been developed and a program has been created for numerical calculation by the smoothed particle hydrodynamics method of the process of deformation of an elastoplastic material in the axisymmetric case in the presence of contact boundaries and thermal conductivity of materials. With the help of this program, the problem of the collision of an aluminum particle with a titanium plate under conditions of cold gas-dynamic spraying is solved. It is shown that during a collision in the vicinity of the contact boundary between a particle obstacle, an aluminum particle is intensely heated up to temperatures of the order of 400oC. The calculated temperature is much lower than the melting temperature of aluminum. An explanation is proposed for the mechanism of the formation of a chemical bond between an aluminum particle and a titanium plate under conditions of cold gas-dynamic spraying due to the formation of an intermetallic compound in a hot layer near the contact boundary due to self-propagating high-temperature synthesis.

An engineering method is proposed for determining the oscillation amplitudes during vortex excitation, taking into account the dependence of the excitation force coefficient, the Strouhal number and the logarithmic decrement of oscillations on the oscillation amplitude of the structure, the distribution of the correlation of aerodynamic force pulsations along the length of the structure, and including the Eurocode method as a special case. It is shown that the developed technique, in contrast to the known ones, makes it possible to more reliably calculate the amplitudes of oscillations of span structures during vortex excitation.

Integral Fourier and Laplace transforms are used to numerically obtain an analytical solution to a quasistatic problem of thermoelasticity for a band with constant properties. Results of numerical calculations are presented.

The mechanisms of excitation of low-frequency unstable combustion of a methane-air mixture in full-scale low-emission combustion chambers are experimentally studied. Experimental investigations of the flow characteristics without combustion in low-emission combustion chambers shows that the central zone of reverse flows can serve as a source of regular hydrodynamic pressure oscillations in a wide range of flow regimes. A model of low-frequency unstable combustion is proposed. The model is based on hydrodynamic instability of the flow in the central zone of reverse flows, which can excite low-frequency regimes of unstable combustion. Methods for suppressing thermohydrodynamic instability of combustion are developed. Based on the proposed model and with the use of methods that ensure suppression of combustion instability, a low-emission combustion chamber with a stable process of combustion in the entire range of its operation conditions is created and tested, which confirms the feasibility of the proposed approach.

An increase in the rate of combustion (gasification) of solid propellants exposed to a sufficiently intense blowing gas flow was discovered experimentally in the 1940s and called erosive burning. Later it was found that for some propellants at relatively low blowing speeds, there may be a decrease in the burning rate, called negative erosion. Attempts to theoretically study negative erosion have been made since 1971 and focused on analyzing changes in the intensity of heat transfer on a burning surface with the leading role of gas-phase reactions, taking into account the effect of large-scale fluctuations in gas velocity and temperature, the effect of the differences in diffusion coefficients and thermal diffusivity of the gas, and the effect of flame stretching. This paper presents an analysis of propellant combustion under blowing conditions in the presence of intense subsurface heat release due to exothermic reactions in the condensed phase. In the case where the surface temperature is limited by the boiling point, local temperature maxima can form in the subsurface layer, leading to an uneven response on the surface and to the occurrence of “intrinsic” turbulence in the adjacent gas layer. This turbulence leads to a change in the heat input to the propellant and allows one to qualitatively explain the effect of negative erosion.

The propagation of a high-temperature synthesis wave through a perforated metal plate mounted inside a cylindrical sample of a powder mixture of Ni + Al was studied experimentally and theoretically. Copper and steel plates of different thickness were used. The passage of the exothermic reaction front through a hole in the barrier was investigated for different thermophysical characteristics of the plate and different geometric dimensions of the hole. Depending on the parameters of the plate, the minimum critical diameter of the hole required for the propagation of the combustion wave in the sample was determined as a function of plate parameters.

The influence of mechanical activation (MA) and Mn content on the rate and maximum combustion temperature, sample elongation during combustion, size of composite particles, mixture yield after MA, phase composition, and morphology of synthesis products in the Ni-Al-Mn system was studied. The mechanical activation of the Ni + Al + Mn mixture expanded the manganese content limit, at which it is possible to realize the combustion of samples without preheating, from 14 to 49 % (wt.). Preliminary MA made it possible to synthesize a compound containing all three initial metals - the (Ni, Mn)Al phase, which is an ordered solid solution of variable composition based on NiAl. In addition, after MA, the burning rate, elongation of product samples and their porosity increased, and the maximum combustion temperature decreased. An increase in the proportion of manganese in the Ni + Al + Mn mixture led to a decrease in the size of composite particles, elongation of product samples, the maximum combustion temperature, and an increase in the yield of the mixture after MA. The dependence of the combustion rate on the proportion of manganese in the activated mixture Ni + Al + Mn has a maximum.

Methods for the selection and analysis of condensed combustion products (CCPs) of large monolithic titanium particles with a diameter of 350 ÷ 460 μm in air at atmospheric pressure are described. Detailed data on the granulometric, morphological, and phase composition of CCPs and the number of particles produced by a single burning mother particle are presented. The following morphological types of CCP particles were identified: compact spheres (combustion residues of mother particles and their fragments) and airgel round and elongated comet-shaped objects (sparse fine particles consisting of chains of nanosized spherules). According to the ratio of O/Ti atoms, all types of CCP particles are oxide particles. The mass fraction of airgel objects in CCPs is 0.52 ÷ 0.98, and their physical density is about 0.8 g/cm³. The characteristic dimensions of compact spheres are 2 ÷ 410 μm, those of airgel round objects are 11 ÷ 470 μm, and the length of airgel comet-shaped objects can reach 13 mm. Typical sizes of spherules are 25 ÷ 100 nm. Large compact spheres 200 ÷ 400 μm in size typically have a gaseous bubble and a density of about 0.9 g/cm³.

Synthesis products in mechanically activated powder mixtures of titanium and nickel of three compositions corresponding to double intermetallic compounds have been studied. The mechanical activation of the mixtures was carried out in a planetary mill at an intensity of 40 g and a processing time of 20 min. The synthesis was carried out in the thermal explosion mode by heating mechanically activated mixtures in a sealed reactor in an argon atmosphere at an average heating rate of 70 ˚C/min. The phase composition of the powder products after synthesis and additional annealing was studied by X-ray diffraction analysis, and the results were discussed using literature data on the temperature dependences of the Gibbs energy of intermetallic compounds. It has been found that, regardless of the elemental composition of the mixtures, the intermetallic compound TiNi₃, which has the highest negative Gibbs energy, is predominantly formed during synthesis. Therefore, a single-phase target product was obtained only from a mixture of composition corresponding to TiNi₃. Thermal explosion products in mixtures of the other two compositions are multiphase. After annealing, the phase composition does not change qualitatively, and the quantitative changes in the phase content are insignificant.

The classical models of steady propagation of combustion and detonation waves in a combustible mixture describe the increase in the system entropy to a maximum value in the case of deflagration (subsonic) combustion of the mixture driven by slow processes of heat conduction and diffusion. In the detonation (supersonic) regime, however, where one of the leading roles belongs to the bow shock wave, the models predict that the combustible system after completion of the chemical reaction “chooses” the minimum increase in entropy. These predictions are inconsistent with the formulation of chemical thermodynamics that the entropy of the system reaches its maximum value after the spontaneous irreversible chemical reaction is finalized and the equilibrium state is established. It is shown in the present study that the predictions of the classical models on the minimum increase in entropy in the case of detonation are eliminated if detonation is considered as a process of combustion of a mixture preliminary subjected to an irreversible process of compression and heating of the initial mixture in the bow shock wave (chemical spike) with a corresponding increase in entropy of the initial mixture and subsequent energy release from the mixture in an irreversible process of mixture conversion to chemical reaction products.

On a pulsed gas detonation apparatus (PGDA) at initial atmospheric pressure, a study was made of the process of initiation and detonation in acetylene-oxygen mixtures C₂H₂ + k O₂, including those with a low content of oxygen near the upper concentration limit of detonation. The cell sizes, detonation velocities, and pressures in the detonation products were measured in the range k from zero to unity, and the composition of the detonation products was calculated. The upper limits of detonation in IGDA barrels with diameters of 14, 26, 46, and 104 mm and the volume of booster charges required to initiate detonation in the limiting modes are found. With regard to hydrogen energy, the technological chain methane ® acetylene ® hydrogen + nanosized detonation carbon is considered and an assessment is made of the characteristics of PGDA as a hydrogen generator.

The previously developed wide-range multiphase equation of state of Fe was used to calculate the shock pressure causing its evaporation during isentropic unloading up to 10^-4 GPa (1 atm). Calculations were made for three initial states of matter: pressure 1 atm and temperature 298 K (“cold” initial state), 1 GPa and 1 500K (“warm” state), and 40 GPa and 4 000 K (“hot” state). The shock pressure is 359, 261, and 132 GPa, respectively. These values are generally lower than the estimates of other authors. Arguments are given in their justification.

The aim of the article is to point out the dangers arising from the properties of plastic dust and what influence its properties have on the origin and course of the explosion. The present study deals with a sample of polyethylene dust, by-product of granulate production and storage. The explosion tests are performed on containers of a similar shape to those found in plants. The volumes of the closed vessels are 1.35 m³ (N1) and 5.45 m³ (N2). The tests are conducted in vessel N1 with a venting area DN 250 on the top of the vessel, in vessel N2 with a venting area DN 585 or DN 775 installed on the upper flanges of the vessels, and in vessels interconnected by pipes with a diameter DN 150 and length of 3, 6, and 10 m. The experiments show that the pressure of the explosion in technological equipment may reach higher values than those obtained in laboratory tests. During the explosion propagation in the connected vessels, the effect of overpressure appears due to precompression; as a result, the measured pressure and the rate of pressure rise are many times higher than the values measured only in the vessel itself with a venting area. As the explosion propagates from a larger volume vessel to a smaller volume vessel, the effect of precompression of the mixture increases the explosion parameters in the smaller vessel despite the opening areas of both vessels. Other elements can be also used to ensure sufficient explosion protection. The results also describe the effect of the length of the pipeline route by which the vessels are connected.

The explosive formability of common age-hardenable Al alloys (2024-T4, 2024-T6, 6061-T4, 6061-T6, 7075-T4, and 7075-T6) is investigated experimentally. Manufacturers utilize explosive forming to produce parts having large and complex geometries in a single operation. To investigate the explosive formability of the most common Al alloys used in the aerospace/aircraft industry, an experimental die design is constructed. Tensile tests are carried out to determine the mechanical behavior of the alloys at low strain rates. Charpy V-notch tests are used as input values to determine the fracture toughness and fracture energy. The strain rate considering the expansion angle is calculated through the analytical formula of the Gurney metal velocity. The strain rates obtained by explosive forming conducted in air are calculated roughly as 1.1·10⁵ s^-1, which is an extreme rate. The experimental results reveal that the 6061-T4 Al alloy could be explosively formed to the demanded geometry without any hollows, cracks, tearing, and fractured regions. It is clear that the T6 temper condition significantly improves the strength of the tested alloys, accompanied by reduction of ductility and crack initiation potential. Except for the 6061-T4 Al alloy, all of the tested alloys are fractured during explosive forming tests. Stereo microscopy and scanning electron microscopy investigations reveal transgranular fracture and cleavage facets resulting from brittle fracture initiated by high strain rates, which occurs in the peak-strength temper condition-T6 of the tested Al alloys.

In 1968-1985, in the course of study of phytobenthos in the Lake Baikal, L.A. Izhboldina sampled and analyzed material on the structure and distribution of meio- and microphytobenthos in Chivyrkuyskiy Gulf, the second-largest gulf in the lake. Until now, just a general description of phytobenthos structure was published. The article presents schemes of 18 profiles, 12 of which (more than three quarters of sampled data) were laid during July 1985. For each profile we have drawn a scheme where indicated dominant and codominant species, type of bottom substrate, generalized biomass of community (gr/m²) and the number of species for every station (sampling site). Due to the predominance of shallow depths and mechanically unstable sandy, silty-sandy and silty substrates, the structure of benthic vegetation is monotonous, and phytobenthos belts described for Lake Baikal, are not expressed. There is also a certain gradient in communities along the central part of the gulf from its top to the mouth. Small bays along the western shore of the gulf have certain specificity. In some parts of the gulf, Chaetomorpha curta (Chlorophyta), Cladophora aegagriopila, C. meyeri, C. meyeri var. gracilior (Chlorophyta), Collema ramenskii (Ascomycota), Gloeothrichia pisum (Cyanophyta), Nostoc pruniforme (Cyanophyta) are comparatively frequent and abundant. Noteworthy, the high occurrence of such algae as G. pisum and C. aegagropila, which are absent in littoral of the open Baikal. Charophyta (Chara sp., Nitella sp.) often form communities at depths of 5-8 m. Among vascular plants, the most active are Lemna trisulca and Potamogeton perfoliatus. The alien North American Elodea canadensis and the zignem algae Spirogyra sp., settled in the lake and experienced catastrophic outbreaks of development in subsequent years, in 1985 were represented by few samples.

Floras of mountain territories are of interest due to their species richness, high level of endemism and a large number of rare species. Mountain ranges situated near geographical boundaries deserve special attention, because their floras are characterized by high diversity due to species of different altitudinal vegetation belts, up to the nival one, as well as due to species intrinsic to different geographical units. The Tsagan-Shibetu Range is one of such ranges. Its Russian part is situated between mountains of the South-Eastern Altai, the Mongun-Taiga Massif and the Tannu-Ola Range. Together with the latter the Tsagan-Shibetu Range delineates the world watershed between the Arctic Ocean basin and the drainless region of the Central Asia. The purpose of this work was to compile a checklist of the flora of the Tsagan-Shibetu Range, to reveal protected species of the flora and species that were not previously indicated for the nature regions of Tuva, to which the territory of the range belongs. To compile the checklist, data from the author’s expeditions in 2004, 2005, 2007, 2011 and 2019 were used (2431 field records and 868 herbarium samples), as well as the herbarium by other botanists collected on the Tsagan-Shibetu Range in 1947-1993 and stored in the Herbarium of the Central Siberian Botanical Garden (NS) (more than 2300 herbarium samples). Electronic databases of field records and herbarium specimen metadata were created by the author in MS Access. They were used in compiling the checklist for obtaining information on the distribution and ecological features of species. The flora of the Russian part of the Tsagan-Shibetu Range comprises 878 species and subspecies of vascular plants, which belong to 300 genera and 70 families. The 10 biggest families are Asteraceae (113 species and subspecies), Poaceae (101), Fabaceae (63), Ranunculaceae (51), Rosaceae (50), Caryophyllaceae (44), Brassicaceae (44), Cyperaceae (41), Scrophulariaceae (35) and Lamiaceae (29). All the ten biggest families are the same as the biggest families of the Boreal Region. The family Fabaceae is one of the three biggest families of the flora, what is peculiar for the Turan floras in the Middle Asia and the flora of Mongolia in the Central Asia. At the same time, these floras are characterized by a large number of species of the family Chenopodiaceae, while in the flora of the Russian part of the Tsagan-Shibetu Range this family is represented by only 15 species and is not among the biggest. These facts demonstrate the borderline nature of the flora of the Russian part of the Tsagan-Shibetu Range which, due to location of the range on the world watershed, shows features of both North Asian and Central Asian floras. Twenty three species of the flora are under state or regional protection and are included into the Red Data Book of the Russian Federation (2008) and/or the Red Data Book of the Tyva Republic (2019) as rare or reducing in number: Aconitum decipiens Worosch. et Anfalov, Allium altaicum Pall., A. pumilum Vved., A. tuvinicum (N. Friesen) N. Friesen, Anoplocaryum turczaninovii Krasnob., Aphragmus involucratus (Bunge) O.E. Schulz, Asterothamnus heteropappoides Novopokr., A. poliifolius Novopokr., Chenopodium frutescens C.A. Mey., Delphinium barlykense Lomon. et Khanm., Euphorbia potaninii Prokh., Microstigma deflexum (Bunge) Juz., Oxytropis acanthacea Jurtzev, O. martjanovii Krylov, O. physocarpa Ledeb., O. trichophysa Bunge, O. tschujae Bunge, Potentilla astragalifolia Bunge, Ranunculus tuvinicus A. Erst, Rheum altaicum Losinsk., Stipa pennata L., Taphrospermum altaicum C.A. Mey., Veronica reverdattoi Krasnob.

Mires are valuable nature conservation complexes with unique biological diversity. The presented work contains the results of studying the floristic diversity of vascular plants in protected mires in the southern part of the Sverdlovsk Region (Russia). The studies were carried out on four peat lowland plain mires: Maloe Lake, Berezovoe, Chernoe (Kamensky District) and Bagaryak (Sysertsky District). Until now, information about the floristic richness of the mires of the southern part of the Sverdlovsk Region has remained fragmentary, and therefore the study allows us to fill in the existing “gaps”. In addition, the studied mires are the southernmost mires of the Sverdlovsk Region within the Trans-Urals, which emphasizes their high environmental significance. The research was conducted in 2021. The territory of each mires was surveyed by the traditional route-reconnaissance method, taking into account the intra-mire hydrographic network. The article provides a list of discovered species of vascular plants. Author’s materials are supplemented with information from the collection of the Museum of the Institute of Plant and Animal Ecology, Ural Branch of the Russian Academy of Sciences (SVER). In total, 188 species of vascular plants belonging to 123 genera, 54 families and 4 divisions were identified in the flora of the studied mires. The leading families in terms of the number of species are Cyperaceae, Asteraceae, Poaceae, Rosaceae, Orchidaceae and Salicaceae. The leading genera are Carex, Salix, Cirsium and Galium. The flora is dominated by plurizonal and boreal species with a wide distribution (Holarctic, European-West Asian and Eurasian). Among the biomorphological groups, polycarpic herbs are of significant importance (145 species, 78 %) of which 45 % are rhizomatous plants. Among the species we have discovered Malus baccata and Carduus acanthoides which are alien and appeared due to ornitho- and anemochory. In the studied mires, cenopopulations of 14 rare species listed in the Red Data Book of the Russian Federation and the Red Data Book of the Sverdlovsk Region were recorded. The work highlights the importance of maintaining mires in a natural state to maintain overall phytodiversity and the possibility of preserving rare and vulnerable plant species.

Genus Epimedium is the largest genus of herbaceous plants in the Berberidaceae family. It includes about 50-65 species. Species of the genus Epimedium have a traditional use in Chinese, Korean and Japanese medicine. They are also known as ornamental plants. Three plant species of Epimedium grow in Russia: E. colchicum (Boiss.) Trautv., E. koreanum Nakai and E. macrosepalum Stearn. All of them are included in the Red Data Book of the Russian Federation. The purpose of the study is a comparative morphological and anatomical study of rhizomes and roots of E. colchicum and E. macrosepalum belonging, respectively, to the subgenera Rhizophyllum and Epimedium. Materials for the study have been collected in the botanical garden of All-Russian Scientific Research Institute of Medicinal and Aromatic Plants. We used an MBS-10 binocular and an Axioplan 2 imaging Carl Zeiss microscope. Cross sections of rhizomes were stained 1) with an alcoholic solution of phloroglucinol and concentrated HCl; 2) 0.1 % cresyl violet solution. Cylindrical rhizomes, non-yearly branching, characterize both species. Rhizomes are dark brown with numerous thin adventitious roots. Rhizomes of E. colchicum are short and thick (diameter 7.8 ± 0.1 mm, length of annual growth 42.9 ± 2.3 mm); rhizomes of E. macrosepalum are thin and elongated (rhizome diameter 2.5 ± 0.1 mm, length of annual growth 65.5 ± 4.8 mm). The zones of the primary bark and the central cylinder on transverse sections of rhizomes are distinguished. Open conducting bundles are located in one circle. The pith is lignified. Idioblasts with druzes of CaC₂O₄ crystals are in the inner zone of the parenchyma of the primary cortex of E. macrosepalum. E. colchicum has relatively wide pith rays (up to 20 rows of cells), the presence of groups of lignified protophloem fibers, and the absence of sheaths of lignified fibers. E. macrosepalum is distinguished by relatively narrow (2-10 rows of cells) pith radiuses, the absence of bundles of lignified protophloem fibers, and the presence of sheaths of lignified fibers.

This paper presents data on the dynamics of the ontogenetic structure of the coenopopulation of Dracocephalum imberbe Bunge, located in the tundra with Dryas oxyodontha Juz. and Kobresia simpliciuscula (Wahlenb.) Mackenz.in Republic of Tuva. Changes in the type of the ontogenetic spectrum and the density index of individuals are analyzed. It was revealed that fluctuating dynamic changes occurred during 17 years, which did not affect the type of ontogenetic spectrum and the normal distribution of ln(n + 1) density. The coenopopulation remains full-fledged. The calculated demographic indicators and indicators of the speed of development reflected a unidirectional type of dynamics towards its gradual rejuvenation.

New syntaxa are described, validation and correction of associations are carried out. New data on the distribution of various syntaxa, their ecology and floristic composition are given. Ass. Alysso tortuosi-Artemisietum salsoloidis Lysenko in Lysenko, Arkhipova et Suleymanova 2020 (Suppl. 1, Table 1, relevés 1, 2). Diagnostic species (D. s.): Artemisia salsoloides (dom.), Pimpinella tragium, Alyssum tortuosum, Matthiola fragrans. The association unites the steppe communities distributed on the chalk slopes of the Volga Upland in the Middle Volga region.

The article is dedicated to the memory of L.V. Bardunov. In 2022, the 90th anniversary from birth of the famous Russian bryologist, florist, Doctor of Biological Sciences, professor, Honored Scientist of the Russian Federation Leonid Vladimirovich Bardunov (1932-2008) was celebrated. L.V. Bardunov made a great contribution to the study of plant biodiversity in North Asia. L.V. Bardunov collected the unique herbarium specimens. Digital copies of 828 specimens collected personally by L.V. Bardunov, or together with M.G. Popov, L.I. Malyshev and other collectors, are placed in the CSBS SB RAS Digital herbarium (http://herb.csbg.nsc.ru:8081). The herbarium specimens are stored in NSK and NS herbarium collections (USU_440537). Each digitized sample is provided with a unique barcode with the acronym of the herbarium collection and a 7-digit serial number. Digitization was carried out according to the international standards at an optical resolution of 600 dpi, accompanied by a color scale and a scale ruler on ObjectScan 1600 scanners, using specialized programs ScanWizard Botany and MiVapp Botany (Microtek). The advanced search for information in the CSBG SB RAS digital herbarium is possible in 9 fields (country, administrative region, habitat, barcode of the herbarium sample, collector, family name, genus name, species name and date of collection). According to L.V. Bardunov’s herbarium specimens, several species of mosses and vascular plants were described. Vascular plants Megadenia bardunovii Popov (Brassicaceae) and Сorispermum bardunovii Popov ex Lomon. (Amaranthaceae Juss.) are named after him. The typification of the name Сorispermum bardunovii was carried out in accordance with the Articles of ICN. This publication is dedicated to the memory of L.V. Bardunov.